The present invention relates generally to contact printing photocopy machines and particularly concerns apparatus for feeding and separating the original and copy sheets in a diazo photocopy machine.
Diazo photocopy machines are well known in the art, U.S. Pat. No. 3,655,184 providing an exemplary disclosure of one such machine. Copying is effected in such machines through a process by which a diazo sensitized copy sheet and an original tracing are arranged in superimposed relation and then fed into the exposure apparatus of the machine. Typical exposure units include a tubular lamp arrangement about which the superimposed sheets are passed to image the light sensitive copy sheet. After exposure, the sheets are separated, with the original sheet exiting the machine and the copy being fed to a developing unit for further processing.
In early diazo photocopy machines the two superimposed sheets exiting from the exposure apparatus were typically manually separated. Automatic sheet separation apparatus were subsequently developed and significantly improved the efficiency with which the machines were operated. For example, the previously mentioned patent discloses an automatic sheet separating apparatus including a pair of feed rollers mounted adjacent the exit area of the exposure apparatus for receiving the exiting superimposed sheets. The rollers are operated at a differential rotational speed for advancing the leading edge of the copy sheet relative to the leading edge of the original. A further roller having a roughened outer surface is provided for deflecting the advanced copy sheet upwardly while the original sheet is guided out of the front of the machine. The upwardly deflected copy sheet is subsequently directed to a developing unit for further processing.
While diazo photocopy machines of the type described above have provided exceptional service through the years, certain aspects of their design and operation have been less than optimal. Initially, the prior art machines are characterized by a relatively large footprint due to the arrangement of the various paper paths through the machine and, particularly due to the upward deflection of the copy sheet by the automatic sheet separator apparatus. Furthermore, failure of proper sheet separation was generally not accounted for and could lead to serious malfunctions in the copy machine.